History is something to be traced back. To answer this question too, we need to go to the cause of the cold war. It was the ideological difference, communism, and democracy that made the separation of the two most powerful superpowers. The United States getting involved in Korea and Vietnam during the cold war was due to the main fact of the ideological difference. America joined the war to fight against communism and provided every aid to Korean and Vietnam. It was more than a help in providing food and materials, as they gave the peasants a chance to fight for their country and gave them a better life.